MySQL Functions with query

🐬 MySQL Functions

(Beginner → Interview Level)

MySQL provides built-in functions to perform calculations, string handling, date operations, and data analysis directly inside SQL queries.

1️⃣ What are MySQL Functions?

MySQL functions are predefined methods that:

  • Take input values

  • Perform operations

  • Return a single value

👉 Used in SELECT, WHERE, HAVING, ORDER BY, etc.

2️⃣ Types of MySQL Functions

Category Examples
Aggregate COUNT(), SUM(), AVG(), MIN(), MAX()
String UPPER(), LOWER(), CONCAT(), LENGTH()
Numeric ABS(), ROUND(), CEIL(), FLOOR()
Date/Time NOW(), CURDATE(), YEAR()
Control IF(), CASE

3️⃣ Aggregate Functions (Most Important ⭐)

 COUNT()

SELECT COUNT(*) FROM students;

 SUM()

SELECT SUM(salary) FROM employees;

 AVG()

SELECT AVG(marks) FROM students;

 MIN() / MAX()

SELECT MIN(age), MAX(age) FROM persons;

4️⃣ String Functions with Queries

 UPPER() / LOWER()

SELECT UPPER(name), LOWER(city) FROM customers;

 CONCAT()

SELECT CONCAT(first_name, ' ', last_name) AS full_name
FROM users;

 LENGTH()

SELECT name, LENGTH(name) FROM products;

5️⃣ Numeric Functions

 ROUND()

SELECT ROUND(12.567, 2);

 ABS()

SELECT ABS(-45);

 CEIL() / FLOOR()

SELECT CEIL(4.2), FLOOR(4.8);

6️⃣ Date & Time Functions ⭐

 NOW()

SELECT NOW();

 CURDATE()

SELECT CURDATE();

 YEAR(), MONTH(), DAY()



 

7️⃣ Control Flow Functions

 IF()

 CASE

8️⃣ Functions in WHERE Clause

9️⃣ Functions with GROUP BY

📌 Interview MCQs (Very Important)

Q1. Which function returns the total number of rows?

A) SUM()
B) COUNT()
C) TOTAL()
D) ROWS()

✅ Answer: B

Q2. Which function converts text to uppercase?

A) UCASE()
B) TOUPPER()
C) UPPER()
D) CAPITAL()

✅ Answer: C

Q3. Which function returns the current date?

A) NOW()
B) CURDATE()
C) DATE()
D) TODAY()

✅ Answer: B

Q4. Which function is used to combine strings?

A) ADD()
B) CONCAT()
C) MERGE()
D) JOIN()

✅ Answer: B

Q5. Which function is used with GROUP BY?

A) WHERE
B) ORDER BY
C) Aggregate functions
D) DISTINCT

✅ Answer: C

Q6. What does AVG() return?

A) Total
B) Maximum
C) Minimum
D) Average

✅ Answer: D

Q7. Which function rounds a number?

A) FLOOR()
B) CEIL()
C) ROUND()
D) FIX()

✅ Answer: C

Q8. Which function checks conditions?

A) IF()
B) CHECK()
C) WHEN()
D) TEST()

✅ Answer: A

🔥 Exam & Interview Tips

✔ Memorize aggregate functions
✔ Practice functions with GROUP BY
✔ Understand CASE vs IF
✔ Functions are heavily used in real queries

✅ Summary

  • MySQL functions simplify data processing

  • Aggregate, String, Numeric, Date functions are crucial

  • Frequently used in SELECT, WHERE, GROUP BY

  • Very important for interviews & exams

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